António Guterres made the appeal late on Friday evening just hours after the United States, France and Britain launched air strikes targeting sites associated with the country’s chemical weapons capabilities.

“There’s an obligation, particularly when dealing with matters of peace and security, to act consistently with the Charter of the United Nations and with international law in general. The UN Charter is very clear on these issues,” Mr Guterres said.

"The Security Council has primary responsibility for the maintenance of international peace and security. I call on the members of the Security Council to unite and exercise that responsibility. I urge all Member States to show restraint in these dangerous circumstances and to avoid any acts that could escalate the situation and worsen the suffering of the Syrian people.”

The joint operation by the US and its allies was in response to a suspected chemical attack in the city of Douma last week.

Mr. Guterres deplored the use of chemical weapons, which he described as “abhorrent.”

Earlier on Friday, the Secretary-General had called on the Security Council to create an independent body to determine who had used chemical weapons in Syria.

Last October, the Council failed to renew the mandate of a UN-OPCW body, known as the Joint Inspection Mechanism, which was established three years ago.

“I have repeatedly expressed my deep disappointment that the Security Council failed to agree on a dedicated mechanism for effective accountability for the use of chemical weapons in Syria,” his statement said.

“I urge the Security Council to assume its responsibilities and fill this gap.”